In conventional single unit circular knitting machines, the sinkers include a nose which is in a high position thereon for knitting a plated pile fabric. The position of the nose and a control ledge on the sinker determines the desired length of the pile because as the pile yarn engages the nose and is caught thereon the yarn is spaced a set distance to the lower ledge defined by the sinker throat so as to establish the height of the formed pile. Typically, in a pile knitting machine, two yarns, a ground yarn and pile yarn, are fed during one cycle of a knitting operation. The two yarns serve as respective upper and lower yarns and are fed by means of appropriate yarn feeders and guides. In accordance with conventional methodology, the first yarn is fed to the needle while the second yarn is fed to the sinker top knitting ledge. Both yarns are caught by the needle hook when the sinker is pushed forward. The lower yarn is received onto the sinker top knitting ledge and the upper yarn is received onto the sinker nose positioned above the sinker top knitting ledge so as to aid in forming the desired height of the plated pile fabric.
As the needle is lowered to a distance below the sinker top knitting ledge, the two yarns received on the sinker form two sinker loops which are spaced according to the vertical distance between the respective parts of the sinker into which the yarns are received. The sinker loop of the upper yarn becomes the pile knit loop and the lower yarn, commonly referred to as the ground yarn, forms the ground knit loop. To knit a plated pile fabric as described above, the ground yarn must be fed to the needle hook and moved by the advancing sinker against the inner side of the needle hook. Additionally, the pile yarn received onto the sinker nose must be retained on the outer side of the needle hook adjacent the latch by the sinker. To form the plated pile fabric, it is necessary to stably position both the pile yarn and ground yarn onto the needle hook.
In accordance with the prior art, three methods conventionally have been used for stable positioning of the ground yarn onto the inner side of the needle hook. In the first prior art method, the sinker includes a throat which forcibly pushes the ground yarn toward the inner side defined by the needle hook so as to position the yarn thereat to form the plated pile knit fabric. In the second method, one of two sinkers inserted into one sinker groove positions the ground yarn onto the inner side defined by the needle hook. The sinker forcibly pushes the yarn to force the yarn into a stable position against the inner side of the needle hook. In the third method, the sinker includes an inclined surface on a top portion thereof which engages the ground yarn to draw the yarn downward. The sinker moves back and forth in a radial direction of the cylinder and forcibly positions the ground yarn onto the inner side of the needle hook. As the ground yarn is forcibly pushed against the inner side of the needle hook, it is stably positioned thereat.
The first and second methods cause yarn breakage in many instances. Additionally, associated knots or lints can be knitted into the fabric to create unacceptable defects. Also, as the ground yarn is positioned on the inner side of the needle hook, it usually is brought into this position by the sinker throat so that the yarn is nipped or caught by the sinker throat and needle. Additionally, if the knit density or the type of yarn must be changed, a skilled operator must make the finite adjustments to the sinker cam for establishing the distance in which the sinker is pushed and for establishing the timing movement of the sinker. This manual operation typically takes a prolonged period and any mistake made in the adjustment of the sinker cam effects the plating property yielded by the pile and ground yarns. Typically, knitting bars also appear along the course direction of the knit. In the third method, the inclined surface of the sinker top knitting ledge pushes the ground yarn. This also can create knitting bars, especially when the distance the sinker travels is incorrectly adjusted.